Part Number:DRV8332
Hello,
We are using the DRV8332 motor driver in a design that is getting ready to go into small quantity production. We need to do a thermal analysis on the design and therefore I need to figure out how much power this chip uses under load.
I'm assuming the 3 phase BLDC motor draws 3A at 24V when being driven under full load. I need some guidance as to calculating the power dissipated in the DRV8332.
My initial idea was to use I^2 * R where R is the Rds_on of the FETs in the driver. I got 80 milli ohms from the data sheet which specifies a single FET so I doubled that to 0.160 Ohms. So, my initial power estimate is 9A*0.160 = 1.44W. This estimate alone doesn't seem to match with our bench testing when analyzing how hot the chip gets and when it over heats and shuts off.
Does anyone have any guidance as to how I could more accurately calculate a power estimate in this situation? Does the PWM waveform/gate driver switching play a role? What other things should I take into account and how would I go about doing that?